Which of the following natural features of a landscape do cities in the developed world modify most often?

Glaciers are large, slow-moving masses of ice primarily found in polar regions and high mountain areas. While they shape landscapes over geological time scales, they are not commonly modified by urban development. The locations conducive to glacier presence are generally remote and less impacted by human activities, making them less relevant to the modifications seen in developed cities.

Mountains are significant natural elevations that are not easily modified by urban development due to their size and stability. While cities may expand into foothills or undertake limited mining and road construction, the core structure of mountains remains largely untouched compared to the extensive alterations seen in river systems.

Plateaus are elevated flatlands that can be modified for agriculture or urban development, but the extent of modification is usually less dramatic than that of rivers. The inherent stability and geological characteristics of plateaus make them less susceptible to frequent or extensive changes compared to the dynamic nature of river systems.